Electrically operated control units are known which may be installed into a lawn sprinkler system, and which may be set so that different groups of sprinklers in the system may be turned on at selected times and turned off after preset watering intervals. The control system and unit of the present invention finds particular utility in lawn sprinkler systems, although its use, as mentioned above, is not limited to such systems.
In the embodiment to be described, the control unit of the invention is a self-contained battery operated system, which is intended to be mounted directly over each manually controlled water valve in the usual lawn sprinkler system, or the like, after the manually operated controller for the valve has been removed. The unit includes an electrically controlled controller for the valve, and a latching solenoid for operating the controller. The unit also includes various manually-adjustable controls, which may be set to cause the unit to turn on the lawn sprinkler system, for example, at a pre-set time each day, and then to turn off the lawn sprinkler after a pre-set watering interval.
The latching solenoid included in the control unit of the invention may be of the type described, for example, in copending application Ser. No. 471,219, which was filed May 20, 1974 in the name of Myrl J. Saarem, and which is assigned to the present assignee. When such a latching solenoid is used, the control unit introduces a turn-on pulse to the solenoid at the pre-set time at which the watering intervals are to begin, and it introduces a turn-off pulse to the solenoid at a pre-set time after the initiation of each watering interval.
The unit of the invention may be simple, compact and inexpensive in its construction, by the inclusion of an electronic integrated circuit chip for establishing the pre-settable timing operations of the unit. The integrated crcuit includes, for example, a counter and simplified logic circuitry, and it serves to count down the output of a crystal controlled oscillator to derive turn-on and turn-off pulses for the latching solenoid from the counter, which pulses may be selected by appropriately manually settable controls for different turn-on and turn-off times.